Index creation problem

I have an interesting problem that I hope someone can help me with. I am running Informix 4.10 on a SCO unix system and am having a problem creating an index. Two indexes already exist on the table: Index 1 is a unique index on fields 1,2,3,4, and 5 Index 2 is a non unique index on fields 4,2,1, and 5 When I try to create on new index on fields 2,3, and 5 I receive an error - 350 Index already exists on column. Any helpful suggestions as to why this is happening would be greatly appreciated. Daniel